In wet-process separator manufacturing for lithium-ion cells, Asahi Kasei SUNFINE UHMWPE UH951 is metered into a co-rotating twin-screw extruder with L/D ≥ 48 and shaft seals rated for solvent-laden feed. The powder is suspended in a paraffinic processing oil; the polymer loading is set within a 10–30 wt% range and adjusted until the gel film leaving the flat die shows no visible agglomerates under 20× polarized-light inspection. A gear pump transfers the gel to a sintered metal screen pack with a nominal retention rating of 10–20 µm before the die. The cast gel film is cooled on a chill roll, extracted with a low-boiling aliphatic solvent to remove the processing oil, stretched biaxially at machine-direction draw ratios above 5× and transverse-direction draw ratios above 4×, and heat-set to stabilize pore structure. Final separator thickness is typically between 5 µm and 20 µm. Tensile strength and elongation are measured on ASTM D882 specimens; melting shutdown behavior is confirmed by differential scanning calorimetry per ISO 11357-3. Pore size characteristics are measured by capillary flow porometry per ASTM F316, with bubble point and mean flow pore size reported for each lot. The separator is ultimately qualified at cell level under IEC 62660-3 or UL 1642 depending on end market. Grade-specific published data for UH951 in wet-process separator lines is limited; initial extrusion trials usually begin with the incumbent grade’s temperature profile and then shift the first three barrel zones by ±5 °C while recording die pressure and gel fracture onset. The final separator is wound into roll stock and assembled into lithium-ion cells after slitting.

What Limits the Hot-Draw Ratio When UH951 Is Used in Gel-Spun Fiber Extrusion?

Because high polymer concentration raises extensional viscosity, the gel-spinning solution for SUNFINE UH951 is prepared at 2–8 wt% in a nonvolatile paraffin or decalin solvent. The powder is first swollen at 40–60 °C for 20–40 min before final heating to 150–180 °C under nitrogen. The solution is filtered through a 10–25 µm sintered metal pack and extruded through a spinneret; the as-spun gel fiber is quenched in a water bath, extracted to remove solvent, and hot-drawn at total draw ratios above 30:1. The resulting fiber is characterized by tenacity above 2.5 GPa and tensile modulus above 100 GPa when tested per ASTM D2256/D2256M. Cut-resistant glove liners containing the fiber are evaluated under EN 388:2016 blade cut and abrasion modules; ballistic panels are tested under NIJ Standard 0101.06 or STANAG 2920 depending on end-market jurisdiction. The main processing conflict is spinneret pressure rise: UH951 may show higher solution viscosity than lower-molecular-weight UHMWPE lots, reducing the operable screw-speed window and increasing the risk of melt fracture at the spinneret entry. If the spinneret pack pressure exceeds 200 bar, the polymer concentration is reduced or the pre-swelling time is extended. Published data for UH951 in commercial gel-spun fiber lines is limited; a spinneret pressure map and at least three concentration trials are required before direct substitution.

For sintered porous sheet and tube stock, SUNFINE UH951 powder is dry-packed into a matched metal mold and compacted at ambient temperature before heating under restraint. Because UHMWPE has no meaningful melt flow rate and is characterized by solution viscosity per ISO 1628-3 or ASTM D4020, sintering is a controlled time-temperature-pressure balance rather than melt fusion. The powder is first sieved into a narrow particle-size fraction; the selected fraction determines the final mean flow pore size, measured by capillary flow porometry per ASTM F316 with isopropyl alcohol as the wetting fluid. Sintering is performed in a circulating air oven at a temperature above the melting peak determined by ISO 11357-3 and below the point of excessive densification; typical heating ramps are 2–5 °C/min, with hold times of 20–45 min per 10 mm of section thickness. Oversintering collapses the pore network, while undersintering leaves weakly fused particles that detach in service. Finished porous parts are used as gas diffusion media, fluidizing plates, silencer elements, and vent plugs. Food-contact porous components are documented against FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011; migration testing follows the intended food-contact temperature. Pore size data are lot-specific and not transferable between different particle-size cuts. Published data for UH951 in sintered porous configurations is limited; pilot sintering trials with a fixed powder fraction are required before mold fill weights and oven profiles are finalized.

Ram Extrusion Die Design and Wear Guide Output Profile

When a reciprocating hydraulic ram is used to produce continuous rectangular and round profiles, SUNFINE UH951 is fed as powder into a heated barrel and pushed into a cooled or lightly heated die where the material is compacted and fused in discrete shots. There is no screw plastication, so output depends on ram frequency, shot weight, and barrel temperature. The barrel temperature is maintained at 200–240 °C; the die land is held at 140–160 °C to control backpressure and prevent melt fracture at the profile surface. Pre-drying is specified at 80 °C for 4 h when storage relative humidity exceeds 60%, because residual moisture creates vapor-induced voids in the heated barrel. The profile is stress-relieved at 80–90 °C for 1 h per 10 mm of thickness before machining. Compliance for food-processing conveyor applications requires the stock to be listed under FDA 21 CFR 177.1520 and, for EU markets, EU Regulation (EU) No 10/2011 with overall migration below 10 mg/dm² under the specified contact conditions. Hardness is checked per ASTM D2240 Shore D; tensile properties of machined specimens are measured per ASTM D638 or ISO 527-2. In service, the profile is mounted with slotted holes or otherwise allowed to accommodate a thermal expansion coefficient of approximately 1.5 × 10^-4 K^-1; rigid fixation across long spans can produce buckling. Published data for UH951 in ram-extruded profiles is limited; die pressure and shot-weight stability should be recorded during the first production run to establish a grade-specific control window.

When Compression-Molded UH951 Replaces Cast Nylon in Bottling Line Star Wheels

For bottling line star wheels and feed screws machined from thick slab, SUNFINE UH951 powder is loaded into a steel mold, compacted at ambient temperature, and heated under hydraulic press pressure to fully densify the part. Mold pressure is held in the range of 10–20 MPa during heating and cooling to prevent void formation and to compensate for the high viscosity of the polymer. Cooling is performed under the same pressure until the mold temperature drops below 60 °C; uncontrolled depressurization during cooling generates internal voids and dimensional warp. The molded blank is machined with carbide-tipped tools at low cutting speeds to avoid local melting at the cut surface. When UH951 replaces cast nylon in bottle handling, clearances are re-evaluated because UHMWPE exhibits a higher thermal expansion coefficient and lower stiffness than cast nylon. Food-contact compliance is documented under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011; specific migration testing is required when wet fatty foods or aggressive cleaning agents contact the plastic. Tensile properties are measured per ASTM D638; hardness is measured per ASTM D2240. Published data for UH951 in compression-molded star wheels is limited; trial plaques should be molded at three pressure levels and checked for void content by ultrasonic scanning or sectioning before full production.

Suction box covers and foil blades for paper machine dewatering sections are machined from SUNFINE UH951 stock where the wear path consists of water, fiber fines, and mineral fillers at headbox temperatures below 60 °C. The sliding contact occurs under a synthetic forming fabric moving at machine speeds above 1000 m/min. Laboratory wet sliding wear is evaluated by a linear reciprocating ball-on-flat tribometer per ASTM G133; the mass loss of UH951 is compared against the incumbent material under the same counterface load and stroke length. The stock is machined from stress-relieved compression-molded or ram-extruded board, with flatness verified after a 24 h conditioning period at 23 °C and 50% RH per ISO 291. Installation requires a mounting system that accommodates thermal expansion of approximately 1.5 × 10^-4 K^-1; fixed rigid mounting across long spans can produce bowing and edge lift. The end product is a suction box cover with machined slots and a precision work surface; slot geometry is produced by CNC machining with carbide tooling. If the same stock is diverted to food-conveyor components, FDA 21 CFR 177.1520 documentation is available from the stock supplier. Published data for UH951 in paper machine dewatering elements is limited; field wear performance is typically validated on a single dewatering station with profilometry before and after 500 h of operation.